Method of forming flanged containers

ABSTRACT

A method of forming a smooth shoulder (16, 14b, 19b), neck (17, 37) and flange (18, 38) at the open end of the cylindrical side wall (12) of a can body (10) comprises the steps of forcing a marginal edge portion (13) of the side wall into at least a first die to form a first portion of reduced diameter having a first shoulder portion (14) and a first cylindrical portion (15); and optionally applying at least one rolling operation to the first portion of reduced diameter, and any further die formed portions of reduced diameter subsequently formed, to generate a smooth shoulder (16, 14, 19b), neck (17, 37) and flange (18, 38). Reference is made to the roll forming process described and claimed in British Pat. No. 1,534,716 as being particularly suitable. The margin-portion (13) is preferably thicker than the rest of the side wall (12).

TECHNICAL FIELD

This invention relates to methods of reducing the diameter of a marginalportion of a cylindrical body to produce a shoulder and neck and moreparticularly but not exclusively to a method of forming a can bodyhaving an outward directed flange on the neck.

BACKGROUND ART

Traditional methods of reducing the diameter of cylindrical bodiesinclude "die necking" in which one end of the cylindrical body is forcedinto a conical die which exerts a compressive force to reduce thediameter and "roll necking" in which a roll is engaged with the exteriorof the cylindrical body as it is rotated to generate the shoulderprofile by a spinning or beading process.

U.S. Pat. No. 3,995,572 describes a method and apparatus for producing aseamless can body with a reduced diameter opening for receiving anaerosol valve. Starting with a cylindrical workpiece a truncated conicalportion supporting a cylindrical portion of reduced diameter is formedby each of a sequence of dies to finally form a shoulder characterizedby the curvilinear configuration imposed by each die. The disadvantageof this series of "die necking" operations is that each die only bringsabout a relatively small reduction in can diameter so that the expenseof several press tools is incurred. Furthermore, the shoulder producedhas a corrugated or stepped shape which is not always desirable.

Beverage cans are now well known in which the top of the side wall isnecked in to receive an aluminium can end of diameter smaller than theoutside diameter of the bulk of the can body. The objective in such cansis to use less aluminium can end material, thus the present inventionalso seeks to provide a method of making neck portions of reduceddiameter.

These prior art cans are usually 2.585" (65.6 mm) diameter necked downto 2.462 (62.5 mm) diameter and made by one of several roll formingmethods currently available.

In one known roll forming method, as described in British Pat. No.1,330,346 (U.S. Pat. No. 3,688,538) a peripheral edge margin of thesidewall of the can body is spun on a mandrel as an external rollcompresses the margin to generate a shoulder neck and flange. However, acollapsible mandrel is required to carry out this method. In anotherroll forming method, as described in our British Pat. No. 1,534,716,(U.S. Pat. No. 4,058,998) the can body is supported in axial compressionwhile a marginal portion adjacent the open end of the body is deformedradially inwards by a pair of external rollers so that the combinationof axial and radial forces generate a shoulder, neck and flange. Thismethod requires only a simple solid chuck, because the neck is formedinto free space.

DISCLOSURE OF THE INVENTION

Accordingly this invention provides a method of forming at least oneshoulder, a neck and a flange at an open end of the cylindrical sidewall of a can body said method comprising the steps (1) successivelyforcing a marginal edge portion defining the open end of the side wallinto one or more dies of reducing diameter to make a portion of reducingdiameter consisting of a corresponding number of shoulder portionssupporting a cylindrical portion; and (2) applying rolls in at least onerolling operation to at least part of the portion of reducing diameterand cylindrical portion to further change the diameter of thecylindrical portion and generate at least one shoulder supporting theneck and flange.

According to a preferred embodiment of the method a pair of rollsapplies a radial force in combination with an axial force on the can ina method claimed according to any of claims 1 to 9 or claim 22 ofBritish Pat. No. 1,534,716. The method may be applied to can bodies ofmaterials which tolerate severe cold work, the method comprising asimple die neck followed by rolling being suitable when the can body ismade of aluminium or alloys thereof. When the can is made of metalswhich are less tolerant of cold work, extra die necking operations maybe included in the method, for example when the body is made of tinplateor stiff aluminium alloy.

Although the die necking operations may not require a thickened sidewall portion, a marginal edge portion thicker than the rest of the sidewall may be used to avoid flange cracking arising from excessive workhardening.

When the rolling method claimed in British Pat. No. 1,534,716 is usedthe diameter of the cylindrical portion to which the roll is applied ispreferably less than that of the diameter of the final flange produced.

The invention further provides a can body having a shoulder neck andflange when produced by the method described.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention will now be described by way ofexample only and with reference to the accompanying drawings in which:

FIG. 1 is a side elevation of an aerosol can produced by a prior art dienecking process;

FIG. 2 is a perspective sketch of a beverage can body broken away toshow side wall thickness;

FIG. 3 is a perspective sketch of the can body of FIG. 2 after formingof the shoulder, neck and flange;

FIGS. 4a, b and c show diagrammatically fragmentary sections of the sidewall at various stages of the formation of a shoulder, neck and flangein a first embodiment of the method;

FIGS. 5a,b,c, & d show diagrammatically fragmentary sections of the sidewall during a second embodiment of the method;

FIG. 6 is a sectioned elevation of part of a die necking tool;

FIG. 7 is a sectioned elevation of part of a roll forming apparatusbefore roll forming.

FIG. 8 is a like view to FIG. 7 but showing the apparatus after rollforming of neck and flange;

FIG. 9 is a like view to FIG. 7 showing apparatus for roll forming acomponent which has been die necked twice; and

FIG. 10 is a fragmentary section of the shoulder, neck and flangeproduced by the apparatus of FIG. 9.

FIGS. 11a,b,c,d, & e show diagrammatically fragmentary sections of theside wall during a third embodiment of the method;

FIG. 12 shows the roll position at the start of neck rolling in themethod of FIG. 11; and

FIGS. 13a,b,c,d,e and f shows diagrammatically the sequence of neckshapes produced by a fourth embodiment of the method.

MODE OF CARRYING OUT THE INVENTION

In FIG. 1 an aerosol can 1 drawn from sheet metal, has a shouldercharacterised by a series of steps 2 each of which was made by a dienecking operation. As depicted the reduced aperture of the top of theshoulder of the aerosol can is closed by a valve cup 3.

FIG. 2 shows a beverage can body 10 such as is produced from a sheetmetal blank by drawing a cup which is then wall ironed to create a canhaving a bottom wall 11 substantially equal in thickness to the blankand side wall 12 thinner than the bottom wall 11. It is customary forsuch can bodies to be formed with a marginal portion 13 of thicker metalaround the open end of the side wall. This marginal portion of metalthicker than the rest of the side wall is better able to tolerateflanging and subsequent fitting of a can end by double seaming. Had thecan body of FIG. 1 been formed by deep drawing to a shallow height, theside wall material would not necessarily be so work hardened as to needthe thicker marginal portion.

FIG. 3 shows the can body of FIG. 2 after the marginal portion 13 hasbeen formed into a shoulder 14, neck 15 and flange 16 by a methodincluding a sequence of die necking and rolling operations.

FIG. 4 shows diagrammatically one embodiment of the method whichincludes the steps of taking a 2.585" (65.6 mm) diameter aluminium alloycan having a side wall ironed to 0.005" (0.127 mm) but provided with athicker margin portion 13 about 0.008" (0.203 mm) thick. The axiallength of the marginal portion is denoted "L" in FIG. 4(a) depends onthe length of the final shoulder, neck and flange to be generated. Thisis because it is desirable to have a shoulder, neck and flange made fromthe thicker marginal material so that it can support the loads arisingduring the seaming on of a can end and thereafter when cans are stackedin transit. In this example the axial length "L" is about 0.55" (14 mm)to permit necking in from the 2.585" (65.6 mm) diameter to a finalinternal neck diameter of 2.360" (59.9 mm). In FIG. 4(b) the marginalportion 13 of FIG. 4(a) has been forced into a die to form a firstportion of reduced diameter having a first shoulder portion 14 whichsupports a first cylindrical portion 15 of internal diameter ofapproximately 2.463" (62.6 mm). The die used for this operation is shownin FIG. 6 and will be described later. In FIG. 4(c) the first portion ofreduced diameter depicted in FIG. 4(b) is depicted after roll forming bymeans of the apparatus of FIGS. 7 and 8, to further reduce the diameterof the first cylindrical portion 15 and generate a smooth shoulder 16supporting a neck 17 and flange 18. The internal diameter of the neck 17is 2.360" (59.9 mm).

Whilst this method described with reference to FIG. 4 is appropriate formetals such as aluminium and its alloys which are tolerant of cold work,metals such as steel and tinplate may require additional die reductionsbefore roll forming to achieve equivalent total reductions in candiameter.

FIG. 5 shows diagrammatically a sequence of operations for the formationof a neck having an internal diameter of 2.260" (57.4 mm) on a wallironed tinplate can body of 2.585" (65.6 mm) diameter. In FIG. 5(a) likeportions of the can body are denoted with the same symbols as usedpreviously.

The side wall 12 is of thickness 0.004" (0.1 mm), the marginal portion13 has a thickness of 0.006" (0.15 mm) and the axial length "L" of themarginal portion 13 is about 0.60" (15 mm). In FIG. 5(b) the marginalportion 13 of FIG. 5.(a) has been forced into a die similar to thatshown in FIG. 6 to make a first portion of reduced diameter having afirst shoulder portion 14(a) supporting a first cylindrical portion15(a) of 2.510" (63.7 mm) diameter. In FIG. 5(c) the first portion ofreduced diameter depicted in FIG. 5(b) has been forced into a second dieto further reduce the diameter of the first cylindrical portion 15(a)and form a second portion of further reduced diameter having a secondshoulder portion 19 and second cylindrical portion 20 of 2.410" (61.2mm) diameter. FIG. 5(d) shows the smooth shoulder 16, neck 17 and flange18 generated by application of a roll to the first and second portionsof reduced diameter depicted in FIG. 5(c).

The method described with reference to FIG. 5 may be adapted to reducethe neck diameter of an aluminium can by use of the reductions tabulatedin TABLE 1, in which the reductions for a tin plate can are shown topermit comparison:

    ______________________________________                                                Starting  First Die Second Die                                                                            Rollneck/                                 "L"     body      Neck      Neck    flange                                    ______________________________________                                                Aluminium                                                             0.495"  2.585"dia 2.480"    2.360"  2.260"                                    (12.6 mm)                                                                             (65.6 mm) (63 mm)   (59.9 mm)                                                                             (57.4 mm)                                         Tinplate                                                              0.600"  2.585"dia 2.510"    2.410"  2.260"                                    (15.2 mm)                                                                             (65.6 mm) (63.8 mm) (612 mm)                                                                              (57.4 mm)                                 ______________________________________                                    

FIG. 6 shows a first die such as is used to make the first portion ofreduced diameter such as those shown in FIGS. 4(b) and 5(b). As theprinciples of such dies are understood in the art and apply to all thediameter reductions considered in this specification, the operation ofonly the one die will be described. In FIG. 6 the apparatus comprises anexternal annular necking die insert 21 supported in an annular housing22, and mandrel 23 movable in an axial direction relative to the dieinsert.

The annular housing 22 has a frustoconical surface 24 which serves tolead the marginal portion 13 of a can body centrally to an inwardlycentered surface 25 of the die insert. The surface 25 of the die insertcontinues to a cylindrical surface 26. The mandrel comprises a centringring 27 having a cylindrical work surface 28 and a support ring 29 whichsupports the centering ring 27. The working surface 28 of the centeringring 27 and the cylindrical surface 26 of the die insert are spacedapart a distance sufficient to permit the deformed marginal portion of acan to pass between until the leading edge of the can abuts the supportring so that the height of the die necked can is controlled as shown inFIG. 6. In use, a can body is pushed into the apparatus so that thesurface 24 guides the leading edge of the marginal portion 13 to theinwardly centred surface 25 of the die insert; the leading edge isdeflected towards the working surface 28 of the centring ring 27 whichin turn directs the leading edge up into the gap between the cylindricalworking surface 28 of the mandrel and the cylindrical surface 26 of thedie insert. Continued upward movement of the can body forms the firstcylindrical portion of the neck until the leading edge abuts the supportring 29. The can is then ejected from the apparatus by moving thesupport ring 29 and centring ring 27 downwards to clear the die insert21. Once the necked can has been ejected the apparatus is returned tothe position depicted in FIG. 6 in readiness for another can body.

FIGS. 7 and 8 show apparatus, for rolling a neck and flange into theside wall of a can body, as is described fully in British Pat. No.1,534,716 (U.S. Pat. No. 4,058,998) to which the reader is directed fora full description. In simple terms the apparatus comprises a chuck 30surrounded by a control ring 31, a lifter pad 32 movable towards andaway from the chuck 30 and a pair of freely rotating work rolls 33 onlyone of which is shown.

In FIG. 7 a can body 10 is depicted just before the work rolls startwork. The can body clamped between the control ring 31 and the lifterpad 32 is held central to an axis of rotation by the chuck 30. The wholeassembly of chuck 30, control ring 31, can 10 and lifter pad 32 arerotated about the axis of rotation and the work rolls 33 are movedradially inwards, by a cam (not shown), towards the axis to bear uponthe shoulder portion 14 and first cylindrical portion 15.

The neck and flange are formed by regulating the downward axial motionof control ring 31 and lifter pad 32 relative to the work rolls 33 togenerate the finished can shoulder 16, neck 17 and flange 18.

It will be noticed that in FIG. 8 the shoulder portion 16 and neck 17are formed into free space, no collapsible mandrel having been used.

FIG. 9 shows how the same apparatus of FIGS. 7 and 8 is used to reform adie necked can having first and second portions of reduced diameter, aswas described with reference to FIG. 5(c), into the finished can havinga smooth shoulder 16, neck 17 and flange 18 of FIG. 10. As shown in FIG.9 the work rolls such as that denoted 33 can be seen to first engagewith the first reduced portion 14(a) as the can rotates. The shoulder,neck and flange are then generated as control ring and lifter pad movedownwards in relation to the chuck. As can best be understood from FIG.8, it will be seen that the peripheral edge of the flange 18 finallyflips outwardly to be formed between an annular recess 34 in the controlring 31 and the upper face of the work rolls 33. For this reason theexternal diameter (denoted Y in FIG. 5(d)) of the flange 18 will begreater than the internal diameter (denoted X in FIG. 5(c)) of the dienecked component presented to the rolling apparatus.

The third embodiment of the method as shown in FIG. 11 comprises takinga can body having a relatively thick rim as shown in FIG. 11(a),subjecting the rim to a sequence of three successive die neckingoperations (FIGS. 11(b), (c) and (i d) and thereafter applying a roll tothat portion of the neck produced by the third die necking operation toform the neck and flange of FIG. 11(e).

The can body of FIG. 11(a) was produced by drawing a cup 2.585".(65.6mm) diameter from a disc cut from a sheet of aluminium alloy 0.0140"(0.36 mm) thick. The alloy of this example was aluminium with about11/4% manganese, however other alloys may be used. The side wall 12 ofthe drawn cup was wall ironed to a wall thickness of about 0.005" (0.13mm) leaving a marginal rim portion 13 some 0.0075" (0.19 mm) thick andan axial length sufficient for the neck and flange. However, if desiredsome of the tapered portion may be formed into the neck.

The first die necking operation reduces the diameter of the marginal rimfrom 2.585" (65.6 mm) to a neck portion 15b about 2.462" (62.5 mm)supported on a first shoulder 14b as shown in FIG. 11(b). The second dienecking operation reduces the diameter of an upper portion of the neckportion 15b of FIG. 11(b) to a neck portion 20b about 2.360" (59.0 mm)supported on a second support 19b as shown in FIG. 11(c). The third dienecking operation reduces the diameter of an upper portion of the neckportion 20b of FIG. 11(c) to a third neck portion 35 of a diameter of2.260" (57.4 mm) supported on a third shoulder portion 36.

In contrast to the method of FIG. 5 in which all the steps in the neckwere rolled to create a smooth neck, in the method of FIG. 11 only theoutermost neck portion 35 and shoulder portion 36 are rolled to create asmooth neck 37 and flange 38. In FIG. 11 the minimum diameter of theneck portion 37 as produced by rolling, is 2.063" (52.4 mm).

The apparatus shown in FIG. 12 works in the same way as the apparatusdescribed with reference to FIGS. 7, 8 and 9. The chuck 30 is enteredinto the can body to support the neck portion 35 while the rolls, suchas that denoted 33, roll the third shoulder portion 36 and neck portion35 into the neck 37 and flange 38 shown in FIG. 11(e).

FIG. 13 shows diagrammatically a fourth embodiment of the method whichmay be applied to tinplate or aluminium bodies. In this embodiment atinplate body is subjected to two die necking operations shown in FIGS.13(b) and 13(c) followed by three rolling operations shown as FIGS.13(d), 13(e) and 13(f).

In FIG. 13(a) the can body has a cylindrical sidewall 12, of diameter2.585" (65.6 mm) defining the mouth of the can. The first and second dienecking operations, the products of which are depicted in FIGS. 13(b)and 13(c), reduce the diameter of the mouth to a diameter of 2.510"(63.8 mm) and 2.410" (61.2 mm) respectively, substantially in the mannerdescribed with reference to FIG. 5.

A rolling operation, as already described with reference to FIG. 5 wasused to produce the flanged body of FIG. 13(d) having an internal neckdiameter of 2.210" (56.1 mm) so producing a flange 39 of diametersmaller than that depicted in FIG. 5. The flange is removed by furtherrolling to produce the can body of FIG. 13(e), the mouth of which isdefined by a cylindrical neck portion 40 of 2.245" (57 mm) diameter.This further rolling causes the slight increase in internal neckdiameter.

Further rolling of the neck portion 40 of the can body of FIG. 13(e)generates a smooth neck of minimum diameter 2.063" (52.4 mm) terminatingin an outwardly directed flange 41 (FIG. 13(f) suitable for doubleseaming to a can end of the 202 size in conventional can makingnomenclature.

From comparison of the embodiments of the method of the invention, itwill be understood that the method may comprise various combinations ofdie necking and rolling operations to form a shoulder, neck and flangeof reduced diameter on a can body.

We claim:
 1. A method of forming a shoulder, neck and flange at an openend of the cylindrical side wall of a can body, comprising a die neckingoperation followed by a rolling operation, wherein the die neckingoperation includes a static die necking step in which a marginal edgeportion defining the open end of the side wall is forced into a die tomake a portion of reduced diameter having a shoulder portion supportinga cylindrical portion, the rolling operation includes a rolling step inwhich the portion of reduced diameter is rolled so as to further reducethe diameter of the cylindrical portion and generate a rereducedshoulder supporting said neck, and forming a flange at a terminal endportion of said cylindrical portion.
 2. A method according to claim 1wherein the die necking operation includes a plurality of said dienecking steps performed in succession each in a separate die and eachproducing a respective one said portion of reduced diameter, and therolling operation includes at least one said rolling step in which atleast the portion of reduced diameter made in the last die necking stepis by rolling reduced to generate said rereduced shoulder supportingsaid neck and said flange.
 3. A method according to claim 1 wherein saidrolling operation comprises supporting the can body in axial compressionwhilst deforming the can body adjacent to said open end by applying anaxial shortening force thereto simultaneously with an inward radialforce.
 4. A method according to claim 3, wherein said can body issupported endwise between a can bottom support element and an axialthrust member, with a terminal edge of said body, defining said openend, engaging said thrust member, relative axial movement being effectedbetween said support element and thrust member to maintain said endwisesupport as the can body is shortened during application of said radialforce.
 5. A method according to claim 3, wherein a pilot element isdisposed with a first tool circumferential tool edge thereof coaxiallywithin said body, said radial force being applied by a second tool edgespaced from said first tool edge by a distance having a constant axialcomponent, said first edge acting as a fulcrum for the deformation ofthe can body.
 6. A method according to claim 5, wherein the second tooledge is moved radially with respect to the can body.
 7. A methodaccording to claim 5, wherein the can body, supported in axialcompression, is subjected to relative axial movement between itself andsaid tool edges, whereby the neck and flange are formed progressivelytowards said terminal edge.
 8. A method according to claim 1, comprisingthe steps of: supporting said can body axially between a can bottomsupport element and an axial thrust member, with a terminal edge of saidbody at its open end engaging said thrust member, and with a pilotelement, having a first circumferential tool edge, disposed with saidfirst tool edge coaxially within the can body; and effecting relativeaxial movement between, on the one hand, the can body, support elementand thrust member, and, on the other hand, said pilot element and aforming element having a second tool edge engaging said can body, whilsteffecting relative radial movement between the can body and said secondtool edge and relative axial movement between said support element andthrust member, so as to continue to support the can body whilstshortening it, whereby at least part of said flange and neck is formedin the can body by said second tool edge with said first tool edgeacting as a fulcrum, said first and second tool edges being maintainedin respective planes at a constant axial spacing from each other.
 9. Amethod according to claim 8, wherein said forming element is a roller,said second tool edge being formed circumferentially thereof, and theroller being rotated about it own axis during formation of the neck andflange.
 10. A method according to claim 8 or 9, wherein the can body isrotated about its own axis by simultaneous rotation of said supportelement and thrust member.
 11. A method according to claim 8 or 9,wherein the said tool edges are maintained in fixed axial planes whilstthe can body, support member and thrust member are moved axially withrespect thereto.
 12. A method according to any one of claims 1 to 9,wherein the can body is made of tinplate or aluminum or aluminum alloy.13. A method according to any one of claims 1 to 9, wherein the marginaledge portion is thicker than the rest of the side wall of the can body.14. A method according to any one of claims 1 to 9, wherein the diameterof the cylindrical portion to which rolls are applied is less than thatof the diameter of the final flange produced.
 15. A method of forming ashoulder, neck and flange on a can body comprising the steps ofproviding a generally frusto-conical forming surface defined by anentrance end surface portion of a greater diameter than an exit endsurface portion with the latter merging with an external cylindricalforming surface in spaced relationship to an internal cylindricalforming surface, providing a can body having a cylindrical side wallincluding a terminal end portion having a diameter greater than that ofthe external cylindrical forming surface, axially aligning the can bodywith the external and internal cylindrical forming surfaces,progressively forcefully axially moving the terminal end portion of thecan body along the entrance end surface portion toward the exit endsurface portion and therebeyond between the external and internalcylindrical forming surfaces under an axial force sufficient totransform the terminal end portion of the can body into a radialshoulder portion and a reduced axial neck portion of a diameter lessthan that of the first-mentioned diameter and establishing apredetermined axial distance between a juncture of said radial shoulderportion and the remainder of the cylindrical side wall and a terminaledge of the reduced axial neck portion, providing at least one externalroller, effecting relative rotation between the roller and the can body,and during the latter progressively forcefully radially inwardly movingthe roller against the reduced neck portion to further reduce thediameter thereof for only a part of the axial distance between theradial shoulder and the terminal edge to form a rolled rereduced neckportion of an axial length shorter than said predetermined axialdistance, and therewith forming a peripheral flange at said terminal endportion.